Question Regarding
MCTs, Coconut Oil and the “Lipid of Choice”
From Reinout on the DD Nutrition Forum:
Just a question about the “never eat a starchy carbohydrate with a saturated fat” remark that gets heard so often.
The idea of avoiding fatty acids in the bloodstream when an insulin spike hits makes complete sense to me. In addition, there’s too much (experimental) information out there to disregard, the question is purely about the understanding.
My problem/misunderstanding, however, is the following. I understood from basic biochemistry and the elegant explanations from Udo Erasmus that fatty acids first get taken up via the lymphatic system and through several mechanisms it takes up to three hours for those fatty acids to reach the blood stream. Similarly the carbohydrates get shuttled into the blood stream straight away (20 minutes or something). Thus there’s a time-gap between the two – why does it matter to not eat carbohydrates and fats at the same time? Shouldn’t it be something like: thou shalt not eat carbs 3 hours after fats?
Response From Dr. Chris Hardy:
reinout,
This is an outstanding question! Thanks for commenting on the article.
Your assessment of carb and fat absorption is absolutely correct. The reason for our statement in the article is the fact that insulin (secreted by a starchy carb load) has both fast and slow effects, with the fast effect occurring in minutes and slow effects occurring in the time frame of hours after initial carbohydrate ingestion.
The fast effect of insulin (minutes) involves activation or inhibition of enzymes involved in metabolism of glycogen, lipids, and protein. Insulin activates enzymes involved in anabolism very quickly. This means that glycogenesis, lipogenesis, and protein synthesis (through augmentation of translation) are “turned on” via activation of already existing enzymes. Catabolic enzymes involved with glycogenolysis (breakdown of glycogen) and lipolysis (breakdown of fat of energy) are inhibited by insulin.
The slow effect of insulin is most germane to your question. Insulin also induces de novo synthesis of the anabolic enzymes mentioned above and suppresses the de novo synthesis of catabolic enzymes (also mentioned above). This means that the metabolic milieu post-insulin will be anabolic (storage) for carbohydrate and available fat for several hours after starchy carbohydrate ingestion.
It does get more complicated depending on amounts of pre-existing glycogen in liver, the amount of starchy carb ingested and insulin sensitivity of the individual, but in general the above discussion
is appropriate.